I think I might have gotten the upper slide from one when I sent my M&P "1.0" back to the factory for a repair. Mine came back with a new slide and the internals were different than my other M&Ps.
The result was that my repaired M&P had the enhanced trigger pull and reset with the factory parts, like it had when I had the Apex trigger parts and reset assist installed on it. Basically, before I sent it back in for repair, I removed all the aftermarket trigger upgrades and when I got it back, didn't need to re-install them. S&W Customer Service made me very happy.
My slide was showing pitting on the breach face. Not really sure the exact cause, but most likely ammo related. Yes, they took care of it for me.